Advancements in the fields of electronics and communications have permitted the introduction and commercialization of many new types of communication systems. Information can be affordably communicated to locations and in manners previously not possible or affordable.
The field of cellular telephony is exemplary of a communication system that has been made possible due to such advancements. A fixed, wireline connection is not required between a transmitting station and a receiving station in a cellular, or other radiotelephonic, communication system to effectuate communications between the stations. Because a "wireless" connection is formed between the transmitting station and the receiving station, use of such a communication system is particularly advantageous to effectuate communications when a wireline connection cannot be conveniently or practically formed.
Various different types of cellular, and other radiotelephonic, communication systems have been implemented and others have been proposed. In many parts of the world, for instance, macrocellular communication networks have been installed. Such networks permit mobile subscriber units positioned anywhere within the area encompassed by the macrocellular networks to communicate pursuant to the macrocellular communication network. A macrocellular communication network typically includes a large number of base stations positioned at spaced-apart locations throughout a geographic area. As a mobile subscriber unit moves throughout the geographical area, communications with the mobile subscriber unit are "handed-off" to successive ones of the base stations. In one type of cellular communication system, a Global System for Mobile (GSM) communications system, control circuitry, including mobile services switching centers (MSCs) and base stations controllers (BSCs), controls communications between the base stations and the mobile subscriber unit. And, location registers, including a home location register (HLR) associated with the mobile subscriber unit, maintain a registry of the positioning of the mobile subscriber unit in a network.
Microcellular communication networks have also been developed and implemented. A Digital Electronic Cordless Telephone (DECT) system is exemplary of a microcellular communication network. A microcellular communication network, analogous to a macrocellular communication network, also permits wireless communications to be effectuated with a mobile subscriber unit. The area encompassed by a microcellular communication network is, however, typically much smaller than the area encompassed by a macrocellular communication network.
The costs associated with a microcellular communication network are generally less than the costs associated with a macrocellular communication network. However, because microcellular communication networks generally encompass limited areas, a single business, or other operator, might be required to construct more than one microcellular communication network to encompass a desired area in which microcellular communications are to be permitted.
For instance, a microcellular communication network might be constructed to provide microcellular communication coverage encompassing a single building. A mobile subscriber unit regularly registered to communicate pursuant to the microcellular communication network must be within the building, i.e., the area encompassed by the microcellular communication network, to communicate therethrough.
It is sometimes desirable to permit a mobile subscriber unit, regularly registered in one microcellular communication network (the "home" network), also to communicate in another microcellular communication network (the "visited" network). For instance, a business might have separate office locations, requiring separate microcellular networks to be installed for each of the separate office locations. It is sometimes desirable, in such instances, to permit personnel regularly located at one of the office locations to be able to communicate by way of a microcellular communication network even when the personnel are temporarily positioned at the other one of the office locations.
By providing communication links between the separate microcellular networks, registration, and other, information pertaining to the mobile subscriber unit stored at the "home" microcellular communication network can be used to permit communications with the mobile subscriber unit, even when the mobile subscriber unit is positioned in an area encompassed by the "visited" microcellular communication network.
Various proposals have been set forth to form communication links between microcellular networks by way of a macrocellular communication network. Such proposals, however, have generally been set forth for purposes of call control and not for purposes of mobility management. Viz. existing proposals for intercoupling the networks have not generally pertained to providing wide-area mobility to mobile subscriber units of microcellular communication networks.
Additionally, existing proposals generally require direct connections between the microcellular and macrocellular communication networks. As the operators of the macrocellular and microcellular communication networks might well be different entities, the conventional requirement for direct connections between the microcellular communication networks might sometimes be problematical.
A manner by which better to provide wide-area mobility to a mobile subscriber unit to increase the mobility permitted of the mobile subscriber unit would be advantageous.
Additionally, a manner by which to provide for the communication of mobility management information between a microcellular and macrocellular communication network without requiring direct connections therebetween would also be advantageous.
It is in light of this background information related to mobility management in a cellular communication system that the significant improvements of the present invention have evolved.